Plastic corner rail and fin-and-tube heating element assembly

ABSTRACT

A FIN-AND-TUBE HEAT EXCHANGER FOR BASEBOARD RADIATORS AND THE LIKE WHEREIN THE FINS HAVE LATERALLY OPENING UNDERCUT NOTCHES OR RECESSES AT THEIR LOWER CORNERS. PLASTIC CORNER RAILS HAVING A THIN SLAT-LIKE, VERTICALLY ORIENTED BODY PORTION ARE ASSEMBLED TO THE FINS ALONGSIDE THEIR LOWER CORNERS BY PAIRS OF INTEGRAL FLEXIBLE FISH HOOK FORMATIONS WHICH FIT INTO AND ARE RETAINED IN THE NOTCHES.

' Sept. 20; 1911 PLASTIC CORNER RAIL AND FIN-AND-TUBE HEATING ELEHENTASSEMBLY Filed llay 8, 1970 United States Patent Oflice Patented Sept.20, 1971 3,605,879 PLASTIC CORNER RAIL AND FIN-AND-TUBE HEATING ELEMENTASSEMBLY Claude William Schaefer, Jr., 119 St. Dunstans Road, Baltimore,Md. 21212 Filed May 8, 1970, Ser. No. 35,837 Int. Cl. F24h 9/08 US. Cl.165-55 4 Claims ABSTRACT OF THE DISCLOSURE A fin-and-tube heat exchangerfor baseboard radiators and the like wherein the fins have laterallyopening undercut notches or recesses at their lower corners. Plasticcorner rails having a thin slat-like, vertically oriented body portionare assembled to the fins alongside their lower corners by pairs ofintegral flexible fish hook formations which fit into and are retainedin the notches.

BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates ingeneral to fin-and-tube heating element assemblies for baseboardradiator structures and like applications, and more particularly to suchfin-and-tube heating element assemblies having plastic corner rails of anovel construction assembled with the fins in a novel manner toaccommodate movement of the fin-and-tube assembly during expansion andcontraction.

In conventional fin-and-tube heating elements, the tube or liquidconduit portion is normally constructed of copper tubing to carry thewater or other liquid heating medium to the heating element and produceheating of the tube and fins to effect thermal exchange with the air andproduce appropriate heating of the room. Such units are frequentlyprovided in baseboard radiator systems, wherein relatively long units orlong installations are provided, usually along the outside walls of eachroom. Customarily, the fin-and-tube heating element assemblies forbaseboard radiators are formed to appropriate lengths for the outsidewall of the room or the heat requirements of the room, and arepositioned with the edges of the fins, or portions of the tubes betweensuccessive fins, on supporting brackets or arms to support thefin-and-tube assembly close to the building wall adjacent the floor ofthe room. A baseboard radiator cover is located outwardly from the wallin covering relation to the fin-and-tube assembly defining an air inletat the floor level below the fin-and-tube assembly and a heated airoutlet at the top of the baseboard radiator unit. Such fin-and-tubeheater units are also used in a number of other types of air heatexchangers.

It will be appreciated that when heat is being demanded in the roomserved by a particular heating element unit and heated water is causedto flow through the copper tubes of the fin-and-tube heating element,the water temperature reaches about 200 degrees F., and the copper tubeexpands approxmately /s of an inch for every 10 to 12 linear feet.Likewise, when the heat demand is satisfied and the thermostaticcontrols terminate flow of heated water through the copper tubes of theheating element, the copper tube contracts as the water temperature inthe tubes returns to approximately room temperature of about 65 degreesF. This expansion and contraction of the heating element has createdparticular problems, such as noise arising during expansion andcontraction, due to sliding of fins over the supporting brackets,possible damage to the edges of the fins or fins which may catch onsurfaces or portions of the supporting brackets during expansion, andpossible distortion of the heating element unit when the construction isunable to freely accommodate the thermal expansion and contraction.

Heretofore, attempts have been made to alleviate this problem byproviding corner tracks assembled at each of the four corners of theplurality of fins in a fin-and-tube heating element assembly, butproblems have persisted as to distortion of the fins or resistance tofree movement of the fins toward and away from each other duringexpansion and contraction of the copper tubes on which they are mounted,because of the frictional restraining force usually present as anincidence to the assembly of the corner tracks on the fins of suchfin-and-tube heating elements. The problem of providing corner railswhich can be readily assembled to the fins of fin-and-tube heatingelements and which still permit appropriate movement of the finsrelative to the rails without undue restraint by the corner rails as thecopper tube expands and contracts has been especially acute when plasticcorner rails are used.

An object of the present invention is the provision of a novel plasticcorner rail and fin-and-tube heating element assembly for baseboardradiator systems and the like wherein the rails serve to reenforce theunit and facilitate handling thereof during installation, and facilitatesupport of the heating element assembly on the conventional railsupports of the radiator unit, wherein the corner rails are made ofplastic having a shape which facilitates their assembly with the finsand permits the fins to freely move relative to the rails on expansionand contraction of the copper tube of the heating element assembly.

SUMMARY OF THE INVENTION The present invention is directed to afin-and-tube heating element assembly for baseboard radiators and thelike wherein the lower corners of each of the fins are provided withslots having an enlarged or undercut portion spaced inwardly from thelateral vertical edges of the fins, communicating by a constricted slotportion with the adjacent vertical fin edge, with the constricted slotportion joining an outwardly divergent or flaring entrance end openingthrough the lateral edges of the fins. A plastic corner rail extendingthe length of the fin-and-tube assembly is provided with a slat-likebody portion in the form of a thin narrow flat strip to lie in avertical plane immediately adjoining the adjacent vertical lateral edgeof the fins with its lower edge extending slightly below the bottoms ofthe fins, and has a pair of generally fish hook shaped projections withthe hook portions extending in relatively opposite directions projectingfrom the slat-like body portion into the slots with the hook portionslying in the enlarged or undercut portions of the slots.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a fragmentary perspectiveview of the plastic corner rail and fin-and-tube heating elementassembly embodying the present invention, showing a representative shortlength of the heating element unit;

FIG. 2 is a fragmentary side elevation view of a short length of theheating element assembly;

FIG. 3 is a perspective view of a length of the corner rail strip,viewed from the inner side thereof;

FIG. 4 is an enlarged cross-section view of the corner rail, taken alongthe line 4--4 of FIG. 3; and

FIG. 5 is a vertical section view through the heating element assembly,taken along the line 5-5 of FIG. 2, and showing the heating elementassembly installed in a typical baseboard radiator unit shown invertical section.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to thedrawings, wherein like reference characters designate correspondingparts throughout the several figures, the heating element assembly ofthe present invention is indicated generally by the reference char acterand comprises a copper tube 11 on which is fitted a plurality of spacedapart fins 12. The fins 12 have a generally rectangular body portion 13with rounded upper corners and have relatively narrow vertical flanges14 at the vertical lateral edges of the body portions and an aperture inthe approximate center of the fin body 13 bounded by an annularcylindrical flange 15 sized to tightly fit on the copper tube 11 and besecured in coaxial surrounding relation to the copper tube 11 in theusual manner.

The lower corner portions of the fins 12 adjacent the lateral edgesthereof are provided with specially shaped slots or notches 16, each ofwhich have an outwardly flaring or divergent entrance portion 16aopening through the lateral edge and flange portion of the associatedfin, a constricted portion 16b spaced inwardly from the edge andcommunicating with the entrance portion 16a, and an enlarged rectangularundercut portion 166 inwardly communicating with the constricted portion16b and defining, in elfect, an undercut recess having restrainingshoulders 17 facing inwardly towards the center plane of the pluralityof fins.

The slots or notches 16 are adapted to receive longitudinally continuousintercoupling projections 19 of plastic corner rail members 20 to couplethe rail members in proper position on the fins 12. The plastic cornerrail members 20 are integral molded extrusions formed from suitableplastic material having a relatively thin narrow slat-like body portion21 defining a continuous elongated strip or rail of uniform heightproviding a lower edge 21a positioned slightly below the bottom edges ofthe fins 12 to rest on support brackets, spaced along the axial lengthof the base board radiator, such for example as the bracket 22illustrated in FIG. 5. The bracket 22, as illustrated, extends outwardlyfrom the building wall 23 and is spaced an appropriate distance abovethe floor 24 to provide a return air inlet 25 below the heating elementassembly 10, and forms the lower support for the front cover panel 26 ofthe baseboard radiator. Additional supporting brackets 27, not relevantto the heating element structure of the present invention, providesupport for the upper edge of the front cover panel 26 and the top coversheet 28, as well as for an adjustable damper 29 in the upper air outletor discharge opening 30.

The rail members 20, as illustrated more particularly in the enlargedcross-sectional View of FIG. 4, has projecting from the slat-like bodyportion 21 at a location about the way up the height of the body portiona pair of vertically spaced intercoupling projections 19 of generallyfish hook shaped cross-sectional configuration, each including a webportion 19a and a hook portion 19b defining a shoulder 190 which isinclined at an acute angle to the plane of the surface of web portion19a which it joins. The two fish hook shaped web portions 19a aresufiiciently flexibly deformable so that they can be readily forced intocoupling relation with the undercut notches or slots 16. This isaccomplished by forcing the fish hook shaped web portions 19 to theleft, with reference to FIG. 4, or inwardly toward the center plane ofthe fins, to bring the rounded portions of the hook formations 19b intoengagement with the flared entrance portion 16a of the notches. Theconverging surfaces of the flared portion 16a force the hook portions 1%toward each other to permit them to pass through the constructed portion16b of the slots 16. When the rails are forced fully to the positionillustrated in FIG. 4, the surface portions 190 of the hook formations19b snap outwardly, due to the elastic memory of the web portions 19,and lap the restraining shoulders 17 of the enlarged portions 160 of therecesses to hold the rail members 20 in assembled relation with thefins.

By this construction, the plastic rails are easily inserted into thenotches of the fins and therefore assembled with the fins of the heatingelements, but the rails are not rigidly connected to the fins orrestrained by frictional pressure against movement to any extent whichwill retard relative movement of the fins toward or away from each otheras the copper tube 11 expands and contracts. It will be appreciated thatthe water in the copper tubes 11 is normally at approximately 65 degreesF., and when heat is demanded in the room or the portion of thebaseboard radiator serving the space sensed by the thermostat, the watertemperature of the heated water which flows through the tubes duringheat demand reaches about 200 degrees F. This causes the copper tubes toexpand approximately /8 of an inch in 10 to 12 linear feet, thusnecessitating some relative movement of the fins 12 away from each otheras an incident to this expansion. The plastic rails, however, stillremain at approximately their normal room temperature, or at least donot get over about 75 degrees F., because the return air stream enteringinlet 25 of the radiator unit below the front cover panel 26 and passingover the plastic rails does not exceed this temperature range. Becauseof the particular construction of the web portions 19 of the railmembers and the configuration of the slots 16, the fins are allowed toreadily move toward and away from each other as required by contractionand expansion of the copper tube 11 without distortion of the heatingelement and without the pinging noises normally caused by expansion andcontraction of heating elements, the fish hook web portions 19 being ofsuch nature that they do not exert suificient restraining frictionalpressure on the fins to hold the fins against movement responsive toexpansion and contraction of the copper tube. Furthermore, the rail isnot easily removed from the fin, thus allowing the fin sections to becut to size easily as well as permitting them to be handled with lesscare than is required with many other units presently available.

What is claimed is:

1. An elongated fin-and-tube heating element unit for baseboardradiators and the like wherein the heating element unit extends along ahorizontal longitudinal axis and is supported on upwardly facinghorizontal surfaces of support brackets; the heating element unitcomprising an axially elongated cylindrical metal tube for conductingheating liquids, a plurality of metal fins arranged in parallel verticalplanes perpendicular to the axis of the tube fixed on the tube with thetube passing through the fins, the fins having aligned horizontal loweredges and respective pairs of opposite vertical lateral edges and havingundercut notches opening outwardly through the opposite lateral edges, apair of corner rails each of integral molded plastic material extendingcontinuously along the length of the plurality of fins at the lowercorners thereof where said lateral edges join said lower edges, thecorner rails each including a slat-like body portion in the form of avertically oriented thin narrow flat strip of generally rectangularcross-section to lie alongside the lower portions of said lateral edgeswith its bottom edge bearing on said surfaces of said support brackets,and a pair of integral fish-hook shaped coupling projections extendinginto said notches, said projections including thin flexible web portionsextending in parallel vertical spaced horizontal planes along the lengthof each respective body portion and having enlarged hook formations onthe inner ends thereof extending in relatively opposite directions intothe undercut portions of said notches to restrain the associated cornerrail against withdrawal while readily permitting relative movement ofthe fins along the longitudinal axis of the corner rail.

2. A fin-and-tube heating element unit as defined in claim 1, whereinthe hook formations of said coupling projections in each corner railhave semi-cylindrical leading surfaces facing toward the longitudinalcenter axis of the unit and define restraining shoulders facingoutwardly toward the lateral edges of the fins and inclined at acuteangles to the web portions.

3. A fin-and-tube heating element unit as defined in claim 1, whereinsaid undercut notches each include a vertically enlarged inner portionsized to accommodate said hook formations, a constricted portionoutwardly adjoining the enlarged inner portion, and an outward flaringdivergent entrance portion outwardly adjoining the constricted portionand opening through the adjacent lateral edge of the associated fin forcamming the hook formations inwardly to pass through said constrictedportion upon insertion of the coupling projections into the notches.

4. A fin-and-tube heating element unit as defined in claim 2, whereinsaid undercut notches each include a vertically enlarged inner portionsized to accommodate said hook formations, a constricted portionoutwardly adjoining the enlarged inner portion, and an outward flaringdivergent entrance portion outwardly adjoining the constricted portionand opening through the adjacent 7 UNITED STATES PATENTS 5/1967 Nelson16555 3,386,501 6/1968 Pastore 16582 3,395,753 8/1968 Falso 16555FREDERICK L. MA'I'I'ESON, JR., Primary Examiner T. W. STREULE, JR.,Assistant Examiner US. Cl. X.R. 165-82

